Add docs

docs/spec/v1beta2/buckets.md

@@ -538,12 +538,15 @@ The query values from the `sasKey` data field in the Secrets gets merged with th
 If the same key is present in the both of them, the value in the `sasKey` takes precedence.
 
 **Note:** SAS Token has an expiry date and it should be updated before it expires so that Flux can
-continue to access Azure Storage. Also, The source-controller requires a bucket-level SAS token since it checks if the bucket exists and this fails with a container-level SAS token.
-The minimum permissions for the SAS Token is:
+continue to access Azure Storage. Also, The source-controller can use a account-level SAS token or a container-level SAS token.
+The minimum permissions for an account-level SAS Token is:
 - Allowed services: Blob
 - Allowed resource types: Container, Object
 - Allowed permission: Read, List
 
+The minimum permissions for a container-level SAS Token is:
+- Permission: Read, List
+
 #### GCP
 
 When a Bucket's `.spec.provider` is set to `gcp`, the source-controller will